For example, Patent Document 1 discloses a power supply unit in which sets priorities of three different types of electric power, namely, clean-generated power, which is generated by using sunlight or wind power as energy, fuel-cell power, which is generated by a fuel cell, and commercial power, which is supplied from an electric power company when supplying them to a power load system. more specifically, the power supply unit is set to preferentially supply the clean-generated power. And the power supply unit additionally supplies the fuel-cell power and commercial power if the clean-generated power is not sufficient to meet power demand of the power load system. This makes it possible to mainly use the clean-generated power as the energy of the power load system, thereby establishing a system that minimizes the influence upon the environment.
For example, Patent Document 2 discloses a system in which produces hydrocarbon (HC) fuel by reacting CO and H2 to Fischer-Tropsch reaction (FT reaction). For example, Patent Document 3 discloses an electrolytic cell comprising an oxygen-ion-conductive film made of a solid oxide electrolyte, and a cathode and an anode disposed on both surface of the film respectively, generating CO and H2 simultaneously by using the electrolytic cell, recovering the generated source gases from the electrolytic cell, and producing HC by reacting the recovered source gases to FT reaction.